Atomic Number 6 Atomic Number 6 Atomic Number 6 What Element is Atomic Number 6? Element atomic number 6 is carbon. Forms of pure carbon include diamond, graphite, and amorphous carbon. Dave King, Getty Images By Anne Marie Helmenstine, Ph.D. Updated September 15, 2015. Carbon is the element that is atomic number 6 on the periodic table . This nonmetal is the basis for life as we know it. Here is interesting trivia and facts about this element: Element Atomic Number 6 Facts Each atom of carbon has 6 protons and electrons. The element naturally exists as a mix of three isotopes. Most of this carbon has 6 neutrons (carbon-12), plus there are small amounts of carbon-13 and carbon-14. Carbon-12 and carbon-13 are stable. Carbon-14 is used for radioisotope dating of organic material. A total of 15 isotopes of carbon are known. Pure carbon can take any of several different forms, called allotropes. These allotropes exhibit markedly different properties.

For example, diamond is the hardest form of any element, while graphite is very soft, and graphene is stronger than steel. Diamond is transparent, while other forms of carbon are opaque gray or black. All of the allotropes of carbon are solids at room temperature and pressure. continue reading below our video Trends in the Periodic Table The element name carbon comes from the Latin word carbo, which means coal. The element symbol for atomic number 6 is C. Carbon is among the elements known in pure form by ancient mankind. Carbon has the highest melting point of the pure elements at 3500 °C (3773 K, 6332 °F). Carbon is the second most abundant element in humans , by mass (after oxygen). Approximately 20% of the mass of a living organism is atomic number 6. Carbon is the fourth most abundant element in the universe . The element forms in stars via the triple-alpha process in which helium atoms fuse to form atomic number 4 (beryllium), which then fuses with atomic number 2 (helium) to form atomic number 6. Carbon on Earth is constantly recycled via the Carbon Cycle .

All of the carbon in your body once existed as carbon dioxide in the atmosphere. Pure carbon is considered non-toxic, although inhaling it can cause lung damage. It has been used since prehistoric time for making tattoos . The tattoos of Otzi the Iceman , a 5300-year-old frozen corpse, were likely made using charcoal. In 1961, the IUPAC adopted the isotope carbon-12 as the basis for the atomic weight system. Atomic number, atomic mass, and isotopes (article) | Khan Academy Atomic number, atomic mass, and isotopes Elements and atoms Atomic number, atomic mass, and isotopes Fundamental properties of atoms including atomic number and atomic mass. The atomic number is the number of protons in an atom, and isotopes have the same atomic number but differ in the number of neutrons. Email Introduction Radioactivity pops up fairly often in the news. For instance, you might have read about it in discussions of nuclear energy, the Fukushima reactor tragedy, or the development of nuclear weapons. It also shows up in popular culture: many superheroes’ origin stories involve radiation exposure, for instance—or, in the case of Spider-Man, a bite from a radioactive spider.

But what exactly does it mean for something to be radioactive? Radioactivity is actually a property of an atom. Radioactive atoms have unstable nuclei, and they will eventually release subatomic particles to become more stable, giving off energy—radiation—in the process. Often, elements come in both radioactive and nonradioactive versions that differ in the number of neutrons they contain. These different versions of elements are called isotopes, and small quantities of radioactive isotopes often occur in nature. For instance, a small amount of carbon exists in the atmosphere as radioactive carbon-14, and the amount of carbon-14 found in fossils allows paleontologists to determine their age. In this article, we’ll look in more detail at the subatomic particles that different atoms contain as well as what makes an isotope radioactive. Atomic number, atomic mass, and relative atomic mass Atoms of each element contain a characteristic number of protons. In fact, the number of protons determines what atom we are looking at (e.g., all atoms with six protons are carbon atoms); the number of protons in an atom is called the atomic number. In contrast, the number of neutrons for a given element can vary.

Forms of the same atom that differ only in their number of neutrons are called isotopes. Together, the number of protons and the number of neutrons determine an element’s mass number: mass number = protons + neutrons. If you want to calculate how many neutrons an atom has, you can simply subtract the number of protons, or atomic number, from the mass number. A property closely related to an atom’s mass number is its atomic mass. The atomic mass of a single atom is simply its total mass and is typically expressed in atomic mass units or amu. By definition, an atom of carbon with six neutrons, carbon-12, has an atomic mass of 12 amu. Other atoms don’t generally have round-number atomic masses for reasons that are a little beyond the scope of this article. In general, though, an atom's atomic mass will be very close to its mass number, but will have some deviation in the decimal places. Since an element’s isotopes have different atomic masses, scientists may also determine the relative atomic mass—sometimes called the atomic weight—for an element.

The relative atomic mass is an average of the atomic masses of all the different isotopes in a sample, with each isotope's contribution to the average determined by how big a fraction of the sample it makes up. The relative atomic masses given in periodic table entries—like the one for hydrogen, below—are calculated for all the naturally occurring isotopes of each element, weighted by the abundance of those isotopes on earth. Extraterrestrial objects, like asteroids or meteors, might have very different isotope abundances. Image showing the "anatomy" of a periodic table entry. At the upper left is the atomic number, or number of protons. In the middle is the letter symbol for the element (e.g., H). Below is the relative atomic mass, as calculated for the isotopes found naturally on Earth. At the very bottom is the name of the element (e.g., hydrogen). Image credit: modified from OpenStax CNX Biology Isotopes and radioactive decay As mentioned above, isotopes are different forms of an element that have the same number of protons but different numbers of neutrons. Many elements—such as carbon, potassium, and uranium—have multiple naturally occurring isotopes.

Carbon-12 contains six protons, six neutrons, and six electrons; therefore, it has a mass number of 12 (six protons plus six neutrons). Carbon-14 contains six protons, eight neutrons, and six electrons; its mass number is 14 (six protons plus eight neutrons). These two alternate forms of carbon are isotopes. Some isotopes are stable, but others can emit, or kick out, subatomic particles to reach a more stable, lower-energy, configuration. Such isotopes are called radioisotopes, and the process in which they release particles and energy is known as decay. Radioactive decay can cause a change in the number of protons in the nucleus; when this happens, the identity of the atom changes (e.g., carbon-14 decaying to nitrogen-14). Radioactive decay is a random but exponential process, and an isotope’s half-life is the period over which half of the material will decay to a different, relatively stable product.

The ratio of the original isotope to its decay product and to stable isotopes changes in a predictable way; this predictability allows the relative abundance of the isotope to be used as a clock that measures the time from the incorporation of the isotope (e.g., into a fossil) to the present. Graph of radioactive decay of carbon-14. The amount of carbon-14 decreases exponentially with time. The time at which half of the original carbon-14 has decayed—and half still remains—is designated as t 1/2. This time is also known as the half-life of the radioisotope and, for carbon-14, is equal to 5730 years. Image credit: modified from CK-12 Biology For example, carbon is normally present in the atmosphere in the form of gases like carbon dioxide, and it exists in three isotopic forms: carbon-12 and carbon-13, which are stable, and carbon-14, which is radioactive.

These forms of carbon are found in the atmosphere in relatively constant proportions, with carbon-12 as the major form at about 99%, carbon-13 as a minor form at about 1%, and carbon-14 present only in tiny amounts 1 ^1 ​1​​start superscript, 1, end superscript. As plants pull carbon dioxide from the air to make sugars, the relative amount of carbon-14 in their tissues will be equal to the concentration of carbon-14 in the atmosphere. As animals eat the plants, or eat other animals that ate plants, the concentrations of carbon-14 in their bodies will also match the atmospheric concentration. When an organism dies, it stops taking in carbon-14, so the ratio of carbon-14 to carbon-12 in its remains, such as fossilized bones, will decline as carbon-14 decays gradually to nitrogen-14 2 Structure of the Atom (grades 6-8) STRUCTURE OF THE ATOM Matter has mass and takes up space. Atoms are basic building blocks of matter, and cannot be chemically subdivided by ordinary means. The word atom is derived from the Greek word atom which means indivisible.

The Greeks concluded that matter could be broken down into particles to small to be seen. These particles were called atoms Atoms are composed of three type of particles: protons, neutrons, and electron. Protons and neutrons are responsible for most of the atomic mass e.g in a 150 person 149 lbs, 15 oz are protons and neutrons while only 1 oz. is electrons. The mass of an electron is very small (9.108 X 10-28 grams). Both the protons and neutrons reside in the nucleus. Protons have a postive (+) charge, neutrons have no charge --they are neutral. Electrons reside in orbitals around the nucleus. They have a negative charge (-). It is the number of protons that determines the atomic number, e.g., H = 1. The number of protons in an element is constant (e.g., H=1, Ur=92) but neutron number may vary, so mass number (protons + neutrons) may vary. The same element may contain varying numbers of neutrons; these forms of an element are called isotopes.

The chemical properties of isotopes are the same, although the physical properties of some isotopes may be different. Some isotopes are radioactive-meaning they "radiate" energy as they decay to a more stable form, perhaps another element half-life: time required for half of the atoms of an element to decay into stable form. Another example is oxygen, with atomic number of 8 can have 8, 9, or 10 neutrons. What are elements? All matter is made up of elements which are fundamental substances which cannot be broken down by chemical means. There are 92 elements that occur naturally. The elements hydrogen, carbon, nitrogen and oxygen are the elements that make up most living organisms. Some other elements found in living organisms are: magnesium, calcium, phosphorus, sodium, potassium. By the late 1800's many elements had already been discovered. The scientist Dmitri Mendeleev, a Russian chemist, proposed an arrangement of know elements based on their atomic mass. The modern arrangement of the elements is known as the Periodic Table of Elements and is arranged according to the atomic number of elements. Here is an Interactive Table of Elements where you can learn more about each of the elements. What makes each element unique?

Every atom would like to have an electron configuration like a noble gases. In noble gases the outer electron shell is complete. This makes the element chemically inert. Helium is an example of a noble (inert) gas. It is not present in organisms because it is not chemically reactive. Historical Models of the atom BOHR MODEL Bohr model shows electrons circling the nucleus at different levels or orbitals much like planets circle the sun. Electrons move from one energy state to another but can only exist aft defineite energy levels. The energy absorbed or released when electrons change states is in the form of electromagnetic radiation. THE WAVE MODEL AND QUANTUM THEORY The Bohr model was only able to explain the very simplest atoms, like hydrogen. Today's modern day theory is based on mathematics and the properties of waves. The wave model forms the basis for the Quantum Theory . This theory gives the probability of locating electrons in a particular location, unlike assuming electrons orbit the nucleus as in the Bohr model. How are electrons organized around the nucleus? All atoms would like to attain electron configurations like noble gases. That is, have completed outer shells. Atoms can form stable electron configurations like noble gases by: sharing electrons gaining electrons.

For a stable configuration each atom must fill its outer energy level. In the case of noble gases that means eight electrons in the last shell (with the exception of He which has two electrons). Atoms that have 1, 2 or 3 electrons in their outer levels will tend to lose them in interactions with atoms that have 5, 6 or 7 electrons in their outer levels. Atoms that have 5, 6 or 7 electrons in their outer levels will tend to gain electrons from atoms with 1, 2 or 3 electrons in their outer levels. Atoms that have 4 electrons in the outer most energy level will tend neither to totally lose nor totally gain electrons during interactions. This Periodic Table of Elements will show you the electron configuration for any element you click on. Visualizing Atomic Orbitals The atomic orbitals of the hydrogen atom can be visualized as a cloud around the nucleus. The orbital represents a probability of finding the electron at a particular location. Darker regions signify a greater probability. Shown below are the 1s (lowest orbital and the 2s orbital. 1s 2s Atomic orbitals do not always have the shape of a sphere. Higher orbitals have very unusual shapes.

2px 3px These orbitals were prepared by Dr. Yue-Ling Wong from the University of Florida for more images click here. Remember molecular orbitals are 3-Dimensional Atoms and Elements Atoms and Elements Atomic Structure Atoms are the basic building blocks of everything around us. They come in different kinds, called elements , but each atom shares certain characteristics in common. All atoms have a dense central core called the atomic nucleus . Forming the nucleus are two kinds of particles: protons , which have a positive electrical charge, and neutrons , which have no charge. All atoms have at least one proton in their core, and the number of protons determines which kind of element an atom is. For example, an oxygen atom has 8 protons. If you were somehow able to change the proton number of this atom to 7, even if everything else remained the same, it would no longer be an oxygen atom, it would be nitrogen. For this reason, we list the different elements by their proton, or atomic, number. The periodic table of elements is a chart of all of the elements that have been discovered so far, in order by their atomic number .

In addition to protons and neutrons, all atoms have electrons , negatively charged particles that move around in the space surrounding the positively-charged nuclear core. Electrons are usually depicted in drawings as much smaller than protons or neutrons because their mass is so much smaller. In fact, electron mass is so small that it is not counted in an atom’s mass. However, the charge strength of a single electron is equal to that of a single proton, and despite their small mass, electrons are important for balancing the charge of an atom. Unless specifically stated otherwise, atoms always have the same number of electrons as protons; therefore, you can find the electron number by looking at the atomic number. But unlike protons, the number of electrons can and does change without affecting the kind of element an atom is! We now know how to find the number of protons and the number of electrons for a given atom, but what about neutrons? How many neutrons do atoms of a given element have? It is NOT always the same as the number of protons and electrons. For example, hydrogen has one proton and one electron, but it doesn’t have any neutrons at all! We determine this by looking at the atomic mass.

Even though an atom is so small it would take almost a million for you to see even a tiny dot on your computer screen, each tiny atom definitely has mass and occupies space. This mass comes from the nucleus. Each proton and neutron has about the same amount of mass, measured in daltons , or atomic mass units (amus). Because the unit of measure is defined by one proton, 1 proton = 1 neutron = 1 dalton = 1 amu. Electrons do have some mass, but it is almost 2000 times less than the mass of a proton. There aren’t enough electrons in any of the atoms we know about to affect the total mass; therefore, the total mass is equal to the sum of the protons and the neutrons in an atom. Because we can find the number of protons and the atomic mass of an atom by looking at its element information in the periodic table, we can calculate the number of neutrons in that atom by subtracting the number of protons from the atomic mass. When the number of neutrons is different for individual atoms of the same element, each atom is called an isotope .

When you read a periodic table, the atomic mass listed is the average atomic mass for all of the isotopes of that element found in nature. For example, carbon has an atomic mass of 12.01 in the periodic table. Carbon can’t have 6.01 neutrons because you can’t have part of a neutron. The value exceeds 6 because, while most carbon atoms have 6 neutrons, some carbon atoms are found with 7 neutrons and others with 8 neutrons. For our purposes, we round the atomic mass to the nearest whole number to calculate the number of neutrons. Atomic Structure This video illustrates how atoms and their components work together. Please enable iFrames to view this content or visit <a href="/html5/kalturaBig.php?id=0_jsdgs6no" target="_blank"> Atomic Structure Video </a>. Please enable iFrames to view this content or visit <a href="/html5/biology/lesson2/Bio02_4A_page2.html" target="_blank">Check Your Understanding </a>. Valence Electrons Now that you’ve had a chance to work with atoms in general, let’s dig a little deeper.

Electrons remain in an atom because of their attraction to the protons’ positive charge, but they are not as tightly associated with the atom as either protons or neutrons. Electrons are complicated particles because they have a lot of space to occupy in an atom, and yet they are also tied to a specific area within that atom. Although the drawings we have been working with show the nucleus as a medium-sized, visible object in the center of an atom, it is actually very tiny, and most of an atom is the space around the nucleus in which the electrons move. Because of their shared negative charge, electrons repel one another if they get too close. At the same time, electrons are attracted to the positive charge of the nucleus. The details of the energy and position of electrons can get really complicated, but we will focus only on what we need to understand to study the molecules of life. Electrons are arranged in energy shells (also known as electron shells ) around the atomic nucleus. Although electrons have plenty of space, they all want to be closest to the positive nuclear charge that is attracting them. At the same time, the electrons repel one another because of their negative charge, and only a few can get close to the nucleus at any given time.

Practically speaking, only two electrons can fit in the three-dimensional space closest to the nucleus. This space is called the first energy shell. If there are three electrons in an atom, the first two will be found in the first energy shell. The third electron will have to settle for the second energy shell, a three-dimensional space a little farther from the nucleus, where it will be alone. In this example, the lone electron is called a valence electron , and the outermost energy shell that contains any electrons is called the valence shell . The second energy shell is big enough to hold as many as eight electrons, grouped in pairs inside four electron orbitals , or spaces where electrons spend most of their time. This means if there is only one electron in the second energy shell, there is a lot of extra space left. When an energy shell is incompletely filled, the electron(s) in that shell are not as stable and are more likely to react. For this reason, atoms tend to react with other atoms in ways that will fill or empty their valence shell to gain the stability of a full outermost energy shell. Atoms can do this by gaining or losing electrons to become ions or by sharing electrons with other atoms to form stable associations.

Using electron number and energy shells, we can determine the number of valence electrons for any given atom and its expected level of reactivity. As you work with the example below, you should remember that although we draw energy shells as circles around an atomic nucleus, this is not meant to represent an actual electron path. The concentric circle style of drawing energy shells is meant to represent the average distance electrons in that energy shell are orbiting the nucleus. In reality, electrons do not move in a circular orbit as depicted in the drawing, but travel much more complicated pathways around an atomic nucleus. Periodic Table of Elements: Los Alamos National Laboratory 2, 4, -4 History From the Latin word carbo: charcoal. Carbon, an element of prehistoric discovery, is very widely distributed in nature. It is found in abundance in the sun, stars, comets, and atmospheres of most planets. Carbon in the form of microscopic diamonds is found in some meteorites. Natural diamonds are found in kimberlite of ancient volcanic "pipes," found in South Africa, Arkansas, and elsewhere. Diamonds are now also being recovered from the ocean floor off the Cape of Good Hope. About 30% of all industrial diamonds used in the U.S.

are now made synthetically. The energy of the sun and stars can be attributed at least in part to the well-known carbon-nitrogen cycle. Forms Carbon is found free in nature in three allotropic forms: graphite, diamond, and fullerines. A fourth form, known as "white" carbon, is now thought to exist. Ceraphite is one of the softest known materials while diamond is one of the hardest. Graphite exists in two forms: alpha and beta. These have identical physical properties, except for their crystal structure. Naturally occurring graphites are reported to contain as much as 30% of the rhombohedral (beta) form, whereas synthetic materials contain only the alpha form. The hexagonal alpha type can be converted to the beta by mechanical treatment, and the beta form reverts to the alpha on heating it above 1000°C. In 1969 a new allotropic form of carbon was produced during the sublimation of pyrolytic graphite at low pressures. Under free-vaporization conditions above ~2550°K, "white" carbon forms as small transparent crystals on the edges of the planes of graphite.

The interplanar spacings of "white" carbon are identical to those of carbon form noted in the graphite gneiss from the Ries (meteroritic) Crater of Germany. "White" carbon is a transparent birefringent material. Little information is presently available about this allotrope. Compounds In combination, carbon is found as carbon dioxide in the atmosphere of the earth and dissolved in all natural waters. It is a component of great rock masses in the form of carbonates of calcium (limestone), magnesium , and iron . Coal, petroleum, and natural gas are chiefly hydrocarbons. Carbon is unique among the elements in the vast number and variety of compounds it can form. With hydrogen , oxygen , nitrogen , and other elements, it forms a very large number of compounds, carbon atom often being linked to another carbon atom. There are close to ten million known carbon compounds, many thousands of which are vital to organic and life processes. Without carbon, the basis for life would be impossible. While it has been thought that silicon might take the place of carbon in forming a host of similar compounds, it is now not possible to form stable compounds with very long chains of silicon atoms.

The atmosphere of Mars contains 96.2% CO2. Some of the most important compounds of carbon are carbon dioxide (CO2), carbon monoxide (CO), carbon disulfide (CS2), chloroform (CHCl3), carbon tetrachloride (CCl4), methane (CH4), ethylene (C2H4), acetylene (C2H2), benzene (C6H6), acetic acid (CH3COOH), and their derivatives. Isotopes Carbon has seven isotopes. In 1961 the International Union of Pure and Applied Chemistry adopted the isotope carbon-12 as the basis for atomic weights. Carbon-14, an isotope with a half-life of 5715 years, has been widely used to date such materials as wood, archaeological specimens, etc. Isotopes About Watch and Favorite Watch Watching this resources will notify you when proposed changes or new versions are created so you can keep track of improvements that have been made. Favorite Favoriting this resource allows you to save it in the “My Resources” tab of your account.

There, you can easily access this resource later when you’re ready to customize it or assign it to your students. Isotopes Isotopes are various forms of an element that have the same number of protons, but a different number of neutrons. Learning Objective Discuss the properties of isotopes and their use in radiometric dating Key Points Isotopes are atoms of the same element that contain an identical number of protons , but a different number of neutrons . Despite having different numbers of neutrons, isotopes of the same element have very similar physical properties . Some isotopes are unstable and will undergo radioactive decay to become other elements. The predictable half-life of different decaying isotopes allows scientists to date material based on its isotopic composition, such as with Carbon-14 dating. Terms Full Text What is an Isotope? Isotopes are various forms of an element that have the same number of protons but a different number of neutrons. Some elements, such as carbon, potassium, and uranium, have multiple naturally-occurring isotopes. Isotopes are defined first by their element and then by the sum of the protons and neutrons present.

Carbon-12 (or 12C) contains six protons, six neutrons, and six electrons ; therefore, it has a mass number of 12 amu (six protons and six neutrons). Carbon-14 (or 14C) contains six protons, eight neutrons, and six electrons; its atomic mass is 14 amu (six protons and eight neutrons). While the mass of individual isotopes is different, their physical and chemical properties remain mostly unchanged. Isotopes do differ in their stability. Carbon-12 (12C) is the most abundant of the carbon isotopes, accounting for 98.89% of carbon on Earth. Carbon-14 (14C) is unstable and only occurs in trace amounts. Unstable isotopes most commonly emit alpha particles (He2+) and electrons. Neutrons, protons, and positrons can also be emitted and electrons can be captured to attain a more stable atomic configuration (lower level of potential energy ) through a process called radioactive decay. The new atoms created may be in a high energy state and emit gamma rays which lowers the energy but alone does not change the atom into another isotope.

These atoms are called radioactive isotopes or radioisotopes. Radiocarbon Dating Carbon is normally present in the atmosphere in the form of gaseous compounds like carbon dioxide and methane. Carbon-14 (14C) is a naturally-occurring radioisotope that is created from atmospheric 14N (nitrogen) by the addition of a neutron and the loss of a proton, which is caused by cosmic rays. This is a continuous process so more 14C is always being created in the atmosphere. Once produced, the 14C often combines with the oxygen in the atmosphere to form carbon dioxide. Carbon dioxide produced in this way diffuses in the atmosphere, is dissolved in the ocean, and is incorporated by plants via photosynthesis . Animals eat the plants and, ultimately, the radiocarbon is distributed throughout the biosphere. In living organisms, the relative amount of 14C in their body is approximately equal to the concentration of 14C in the atmosphere. When an organism dies, it is no longer ingesting 14C, so the ratio between 14C and 12C will decline as 14C gradually decays back to 14N.

This slow process, which is called beta decay, releases energy through the emission of electrons from the nucleus or positrons. After approximately 5,730 years, half of the starting concentration of 14C will have been converted back to 14N. This is referred to as its half-life, or the time it takes for half of the original concentration of an isotope to decay back to its more stable form. Because the half-life of 14C is long, it is used to date formerly-living objects such as old bones or wood. Comparing the ratio of the 14C concentration found in an object to the amount of 14C in the atmosphere, the amount of the isotope that has not yet decayed can be determined. On the basis of this amount, the age of the material can be accurately calculated, as long as the material is believed to be less than 50,000 years old. This technique is called radiocarbon dating , or carbon dating for short. Atomic Number and Mass Number About Watch and Favorite Watch Watching this resources will notify you when proposed changes or new versions are created so you can keep track of improvements that have been made.

Favorite Favoriting this resource allows you to save it in the “My Resources” tab of your account. There, you can easily access this resource later when you’re ready to customize it or assign it to your students. Atomic Number and Mass Number The atomic number is the number of protons in an element, while the mass number is the number of protons plus the number of neutrons. Learning Objective Determine the relationship between the mass number of an atom, its atomic number, its atomic mass, and its number of subatomic particles Key Points Neutral atoms of each element contain an equal number of protons and electrons . The number of protons determines an element's atomic number and is used to distinguish one element from another. The number of neutrons is variable, resulting in isotopes , which are different forms of the same atom that vary only in the number of neutrons they possess. Together, the number of protons and the number of neutrons determine an element's mass number . Since an element's isotopes have slightly different mass numbers, the atomic mass is calculated by obtaining the mean of the mass numbers for its isotopes. Terms Full Text Atomic Number Neutral atoms of an element contain an equal number of protons and electrons.

The number of protons determines an element's atomic number (Z) and distinguishes one element from another. For example, carbon's atomic number (Z) is 6 because it has 6 protons. The number of neutrons can vary to produce isotopes, which are atoms of the same element that have different numbers of neutrons. The number of electrons can also be different in atoms of the same element, thus producing ions (charged atoms). For instance, iron, Fe, can exist in its neutral state, or in the +2 and +3 ionic states. Mass Number An element's mass number (A) is the sum of the number of protons and the number of neutrons. The small contribution of mass from electrons is disregarded in calculating the mass number. This approximation of mass can be used to easily calculate how many neutrons an element has by simply subtracting the number of protons from the mass number. Protons and neutrons both weigh about one atomic mass unit or amu. Isotopes of the same element will have the same atomic number but different mass numbers.

Atomic Number and Mass Number ATOMIC NUMBER AND MASS NUMBERS After reading this section you will be able to do the following: Define and determine the atomic number of an atom. Define and determine the mass number of an atom. What is an atom's atomic number? The number of protons in the nucleus of an atom determines an element's atomic number. In other words, each element has a unique number that identifies how many protons are in one atom of that element. For example, all hydrogen atoms, and only hydrogen atoms, contain one proton and have an atomic number of 1. All carbon atoms, and only carbon atoms, contain six protons and have an atomic number of 6. Oxygen atoms contain 8 protons and have an atomic number of 8. The atomic number of an element never changes, meaning that the number of protons in the nucleus of every atom in an element is always the same. What is an atom's mass number? All atoms have a mass number which is derived as follows. Review: An element's or isotope's atomic number tells how many protons are in its atoms. An element's or isotope's mass number tells how many protons and neutrons in its atoms.

The Element Hydrogen -- Hydrogen Atom 3H SI units & STP are used except where noted. In the laboratory, hydrogen is prepared by reaction of acids on metals such as zinc. For production in large scale commercial bulk hydrogen is usually manufactured by decomposing natural gas. Electrolysis of water is a simple although inefficient method. Scientists are now researching new methods for hydrogen production. One of them involves use of green algae. Another promising method involves the conversion of biomass derivatives such as glucose or sorbitol, which can be done at low temperatures through the use of a new catalyst. Notable characteristics Hydrogen is the lightest chemical element with its most common isotope consisting of just a single proton and electron. At standard temperature and pressure conditions, hydrogen forms a diatomic gas, H2, with a boiling point of only 20.27 K and a melting point of 14.02 K. Under exceedingly high pressures, like those found at the center of gas giants, the molecules lose their identity and the hydrogen becomes a liquid metal (see metallic hydrogen).

Under the exceedingly low pressure conditions found in space, hydrogen tends to exist as individual atoms, simply because there is no way for them to combine; clouds of H2 form and are associated with star formation. The hydrogen atom A hydrogen atom is an atom of the element hydrogen. It is composed of a single negatively charged electron, moving around the positively charged proton which is the nucleus of the hydrogen atom. The electron is bound to the proton by the Coulomb force. Applications Large quantities of hydrogen are needed industrially, notably in the Haber process for the production of ammonia, the hydrogenation of fats and oils, and the production of methanol. Hydrogen is used in hydrodealkylation, hydrodesulfurization, and hydrocracking. Other uses: The element is used in the manufacture of hydrochloric acid, welding, and the reduction of metallic ores. It is used in rocket fuels. Liquid hydrogen is used to perform cryogenic research, includingsuperconductivity studies. Since hydrogen is fourteen and a half times lighter than air, it was once widely used as a lifting agent in balloons and airships. However this use was curtailed when the Hindenburg disaster convinced the public that the gas was too dangerous for this purpose.

Deuterium, an isotope (hydrogen-2) of hydrogen, is used in nuclear fission applications as a moderator to slow down neutrons, and is also used in nuclear fusion reactions. Deuterium compounds have applications in chemistry and biology in studies of reaction isotope effects. Tritium (hydrogen-3), produced in nuclear reactors, is used to construct hydrogen bombs. It is also used as an isotopic label in the biosciences and as a radiation source in luminous paints. Hydrogen can be burned in internal combustion engines, and a fleet of hydrogen-burning cars is maintained by Chrysler-BMW. Hydrogen fuel cells are being looked into as a way to provide potentially cheap, pollution-free power. History Hydrogen (French for water-maker, from Greek hudï¿½r, "water" and gennen, "generate") was first recognized as a distinct substance in 1776 by Henry Cavendish. Antoine Lavoisier gave the element its name. Occurrence Hydrogen is the most abundant element in the universe, making up 75% of normal matter by mass and over 90% by number of atoms.

This element is found in great abundance in stars and gas giant planets. Relative to its great abundance elsewhere, hydrogen is very rare in the earth's atmosphere (1 ppm by volume). The most common source for this element on earth is water which is composed two parts hydrogen to one part oxygen (H2O). Other sources include most forms of organic matter (currently all known life forms), coal, fossil fuels and natural gas. Methane (CH4), which is a byproduct of organic decay, is an increasingly important source of hydrogen. Hydrogen can be prepared in several different ways: steam on heated carbon, hydrocarbon decomposition with heat, reaction of a strong base in an aqueous solution with aluminium, water electrolysis, or displacement from acids with certain metals. Commercial bulk hydrogen is usually manufactured by decomposing natural gas. Compounds The lightest of all gases, hydrogen combines with most other elements to form compounds. Hydrogen has an electronegativity of 2.2, so it forms compounds where it is the more non-metallic and where it is the more metallic element.

The former are called hydrides, where hydrogen either exists as H- ions or just as a solute within the other element (as in palladium hydride). The latter tend to be covalent, since the H+ ion would be a bare nucleus and so has a strong tendency to pull electrons to itself. These both form acids. Thus even in an acidic solution one sees ions like hydronium (H3O+) as the protons latch on to something. Hydrogen combines with oxygen to form water , H2O, and releases a lot of energy in doing so, burning explosively in air. Deuterium oxide, or D2O, is commonly referred to as heavy water. Hydrogen also forms a vast array of compounds with carbon . Because of their association with living things, these compounds are called organic compounds, and the study of the properties of these compounds is called organic chemistry. Forms Under normal conditions hydrogen gas is a mix of two different kinds of molecules which differ from one another by the relative spin of the nuclei. These two forms are known as ortho- and para-hydrogen (this is different from isotopes, see below).

In ortho-hydrogen the nuclear spins are parallel (form a triplet), while in para they are antiparallel (form a singlet). At standard conditions hydrogen is composed of about 25% of the para form and 75% of the ortho form (the so-called "normal" form). The equilibrium ratio of these two forms depend on temperature but since the ortho form has higher energy (is an excited state), it cannot be stable in its pure form. In low temperatures (around boiling point), the equilibrium state is comprised of almost only para form. The conversion process between the forms is slow and if hydrogen is cooled down and condensed rapidly, it contains large quantities of the ortho form. It is important in preparation and storage of liquid hydrogen since the ortho-para conversion produces more heat than the heat of its evaporation and a lot of hydrogen can be lost by evaporation in this way during several days after liquifying. Therefore, some catalysts of the ortho-para conversion process are used during hydrogen cooling. The two forms have also slightly different physical properties. For example, the melting and boiling points of parahydrogen are about 0.1 K lower than of the "normal" form.

Isotopes The most common isotope of hydrogen is 1H. This stable isotope has a nucleus consisting of a single proton; hence the descriptive, although rarely used, name protium for 1H. The other stable isotope is deuterium, 2H, with an extra neutron in the nucleus. Deuterium comprises 0.0184-0.0082% of all hydrogen (IUPAC); ratios of deuterium to protium are reported relative to the VSMOW standard reference water. The third hydrogen isotope is the radioactive tritium, 3H. The tritium nucleus contains two neutrons in addition to the proton. Hydrogen is the only element that has different names for its isotopes. The symbols D and T (instead of 2H and 3H) are sometimes used for deuterium and tritium, although this is not officially sanctioned. (The symbol P is already in use for phosphorus and is not available for protium.) Precautions Hydrogen is a highly flammable gas burning at concentrations as low as 4%. It also reacts violently with chlorine and fluorine .

Hydrogen, when mixed with oxygen and lit, burns with an explosion. Some or all of this text has been obtained from Wikipedia, the free encyclopedia. All text in this document is available under the terms of the GNU Free Documentation License (see Copyrights for details). Disclaimers . Wikipedia is powered by MediaWiki , an open source wiki engine.

Question: Which atom, with atomic number 6, is present in all known life forms?
Answer: Carbon